Photographic emulsions and processes

ABSTRACT

Chemically developable photosensitive aurous iodide emulsions are described. Photosensitive elements prepared from the aurous iodide emulsions can be developed with conventional silver halide developers and by diffusion transfer processes.

United States Patent [72] inventors PeterJ.H1llson [54] PHOTOGRAPHIC EMULSIONS AND PROCESSES 15 Claims, No Drawings [52] US. Cl 96/88 [51] int Cl G03c 1/00 [501 Field oismii [56] References Cited UNITED STATES PATENTS 2,624,674 1/1953 Tarkington et al. 96/108 3,408,196 10/1968 McVeigh 96/108 Primary Examiner-Norman G. Torchin Assistant Examiner-John L. Goodrow Att0rneysWilliam H. .I. Kline, James R. Frederick and Joshua G. Levitt ABSTRACT: Chemically developable photosensitive aurous iodide emulsions are described. Photosensitive elements prepared from the aurous iodide emulsions can be developed with conventional silver halide developers and by diffusion transfer processes.

PHOTOGRAPHIC EMULSIONS AND PROCESSES This invention relates to photographic emulsions and to methods of obtaining photographic images therewith. In a particular aspect it relates to photographic emulsions employing a gold salt as the photosensitive component.

The chemical inertness of gold makes it desirable for use in applications where an extremely stable and inert image is required. Certain gold salts are known to give a printout image if exposed to suitable sources of actinic radiation for relatively long periods of time. Gold salts have also been employed in conjunction with silver halide emulsions and have been used in such emulsions as sensitizers, stabilizers, and the like. However, to our knowledge, chemically developable emulsions employing gold salts as the sole photosensitive component have not previously been employed.

It is an object of this invention to provide novel photosensitive emulsions containing aurous iodide as the photosensitive component.

It is a further object of this invention to provide chemically developable photosensitive aurous iodide emulsions.

It is another object of this invention to provide a process for preparing gold images from a photosensitive aurous iodide emulsion by chemical development.

It is yet another object of this invention to provide a diffusion transfer process for preparing gold images from a photosensitive aurous iodide emulsion.

The above and other objects of this invention will become apparent to those skilled in the art from the further description of the invention which follows.

According to the present invention there is provided a photosensitive emulsion comprising a dispersion of aurous iodide grains in a hydrophilic colloid. The emulsions of the present invention can be coated and exposed in a manner similar to that employed with silver halide emulsions and can be processed by treatment with certain conventional silver halide developing solutions, or with other reducing agents, such as hypophosphorous acid solution, followed by washing. No separate fixation step is necessary since the developer solution acts as a monobath due to the solubility of aj'urous iodide therein. Images can also be produced by diffusion transfer methods.

The hydrophilic colloid employed in the emulsions of the present invention can be any of the known hydrophilic waterpermeable binders suitable for photographic purposes and include, for example, gelatin such as bone gelatin, pigskin gelatin, phthalated gelatin, etc., cellulose derivatives such as carboxymethyl cellulose, cellulose ether phthalates, etc., polymerized vinyl compounds such as polyvinyl alcohol, polyvinyl acetates, polyvinyl phthalates, etc., as well as mixtures of such binders. These binders can also contain waterinsoluble materials such as waterinsoluble acrylate and methacrylate polymers. A preferred hydrophilic colloid is gelatin.

The aurous iodide emulsions of the present invention can be prepared by mixing an auric salt, such as sodium auric chloride, with a molar excess of an iodide, such as a potassium iodide, with or without the presence of a protective colloid. After precipitation of the aurous iodide the emulsion can be washed and filtered to remove soluble impurities.

The emulsion can contain a variety of photographic addenda known to those skilled in the art and utilized for their known purpose, such as surfactants and coating aids, agents to modify the flexibility of the emulsion, agents to modify its surface characteristics, agents to modify the adhesivity of the emulsion to a support, and the like.

The aurous iodide emulsion can be coated on a support by such techniques as dip coating, whirl coating, doctorblade coating, hopper coating, etc. Useful results are obtained when the aurous iodide emulsion is coated at a rate of between about to 800 milligrams of aurous iodide per square foot of support. A coating rat of 40 to 400 milligrams of aurous iodide per square foot of support is preferred.

The aurous iodide emulsions of the present invention can be coated on any of the known photographic supports. Suitable support materials include fiber base materials such as paper, polymercoated paper (e.g., polyethylene-coated paper, polypropylenecoated paper), parchment, cloth, etc.; sheets and foils of such metals as aluminum, copper, magnesium, zinc, etc.; glass, ceramic materials, synthetic polymeric materials such as polyalkyl methacrylates (e.g., polymethyl methacrylate), polyester film base (e.g., polyethylene terephthalate), polyvinyl acetals, polyamides, (e.g., nylon), cellulose ester film base (e.g., cellulose nitrate, cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate and the like.

Photosensitive elements containing the aurous iodide emulsions of the present invention can be exposed for lengths of time and to light sources known to those skilled in the art and generally applicable to photosensitive elements containing silver halide emulsions. Exposure times of from a fraction of a second to several minutes or longer are generally useful. The exact exposure time can be determined by those skilled in the art by consideration of such factors as the exposure source, its intensity, the density of the image to which the emulsion is being exposed, etc. Suitable exposure sources include tungsten lamps, carbon arc lamps, xenon lamps, quartz iodide lamps, and the like.

The exposed elements can be developed with solutions of certain conventional silver halide developers, such as polyhydroxybenzene developers (e.g., hydroquinone), and aminophenol developers (e.g., methylaminophenols), as well as with solutions of such reducing agents as hypophosphorous acid.

Various addenda, known to those skilled in the art, can be incorporated for their known effect in the developers useful in the present invention. These include development activators, buffers, antifoggants, preservatives, thickening agents, and the like.

The temperatures which are normally employed in silver halide photographic processing can be employed in developing photosensitive elements of this invention containing an aurous halide emulsion. Processing can be carried out at ambient temperatures, such as between 20 and 30C., and at elevated temperatures, such as above about 50C., e.g., 50to C. Suitable temperatures can be determined by those skilled in the art.

The time of development can vary from a few seconds to an hour or more, depending upon the processing conditions and the desired image. The optimum time can be readily determined by those skilled in the art based on the eiement to be processed, the temperature of processing, the various addenda present in the processing compositions, etc.

The photosensitive elements of the present invention can also be developed by diffusion or solvent transfer processes, which are well known in connection with the development of silver halide emulsions. Rott in US. Pat. No. 2,352,014 described such a transfer process for preparing reversal images. In the Rott process an exposed photographic silver halide emulsion is impregnated with a developer and is pressed in contact with a receiving sheet in the presence of a silver halide solvent and a fogging agent. The undeveloped silver halide in the emulsion layer is transferred by means of the silver halide solvent to the receiving sheet, the transferred silver halide developing to silver to form a positive image on the receiving sheet. Other investigators in this field, such as Land, suggested the use of various specific fogging agents or nuclei that could be used in the reception layer to facilitate the formation of a silver image therein and the use of viscous processing materials to facilitate the utilization of processing materials in pods positioned between the lightsensitive negative layer and the reception layer.

In developing the photosensitive elements of this invention by a diffusion transfer process, a solution of one of the developers mentioned above is employed. Since the developer 5 solution is a solvent for the aurous iodide, a separate aurous iodide solvent need not be employed to effect transfer from unexposed areas of the element to the receiving sheet.

Conventional silver halide receiving sheets employing a wide variety of nuclei or precipitating agents can be utilized in the diffusion transfer processes of this invention. Such nuclei are incorporated into conventional photographic organic hydrophilic colloid layers and include such physical nuclei or chemical precipitants as heavy metals, especially in colloidal form and salts of these metals; salts, the anions of which form gold salts less soluble than the aurous iodide of the photographic emulsions, and nondiffusing polymeric materials with functional groups capable of combining with an insolubilizing aurous ions. Typically useful precipitating agents include sultides, selenides, polysulfides, polyselenides, thiourea and its derivatives, mercaptans, stannous halide, silver, gold, platinum, palladium, mercury, colloidal silver, aminoguanidine sulfate, aminoguanidine carbonate, arsenous oxide, sodium stannite, substituted hydrazines, xanthates, and the like. Other precipitating agents will occur to those skilled in the present art.

The following examples further illustrate this invention.

EXAMPLE 1 Under safelight conditions 1.25 cc. of a (LS-molar sodium auric chloride solution is rapidly added to 1 cc. of a 1.5- molar potassium iodide solution. After 30 seconds 15 cc. of a 10 percent gelatin solution at 40C. is added, shaken for 30 seconds and coated on a photographic paper support at a coverage of about 12 cc. of emulsion per square foot of support. The element is imagewise exposed to a 250- watt phototlood lamp at a distance of 1 foot for 5 seconds and processed for 5 minutes at 20 C. in a developer solution having the following formulap methylaminophenol sulphate 2.2 grams sodium sulphate (anhydrous) 75.0 grams hydroquinone 17.0 grams sodium carbonate (anhydrous) 65.0 grams potassium bromide 2.8 grams water to make L liter A gold image is formed in exposed areas of the element.

EXAMPLE 2 The procedure of example 1 is repeated but 1 cc. of a 10 percent Triton X 200 solution (an anionic surfactant) is added to the potassium iodide solution before addition of the sodium auric chloride solution. (Triton is a registered trademark.) A similar image is obtained.

EXAMPLE 3 The procedure of example 2 is followed but 1 cc. of a 2.5 solution of a polymer of a methyl vinyl ether of maleic anhydride is used in place of Triton X 200. Similar results are obtained.

EXAMPLE 4 The procedure of example 2 is followed but 1 cc. of a 10 percent gum arabic solution is used in place of Triton X 200 Similar results are obtained.

EXAMPLE 5 The procedure of example 2 is followed but 1 cc. of a percent of a copolymer of N-(3- thiabutyl)acrylamide and 3- acryloxypropane---- sulphonic acid sodium salt (ratio 1:6) is used in place of Triton X 200. Similar results are obtained.

EXAMPLE 6 The procedure of example 5 is followed but the ratio of monomers in the copolymer is 1:9.

EXAMPLE 7 The procedure of example 6 is followed but 0.l cc. of copolymer solution is used. Similar results are obtained.

EXAMPLE 8 The elements prepared in examples l-7 are exposed and processed for 2 minutes at 20 C. in a 50 percent hypophosphorous acid solution. Similar results are obtained.

EXAMPLE 9 The coated elements prepared in examples l-7 are exposed as in example 1, wet with a 12 percent hypophosphorous acid solution and at once are pressed face down in contact with a nucleated receiving sheet (Kodak C.T. offset foil). The emulsions transfer to the foil and on washing off in hot water the areas in contact with unexposed areas of the elements are found to be darker than the areas in contact with exposed areas of the elements.

EXAMPLE 10 The precipitation of aurous iodide can with advantage be carried out in the presence of a mild reducing agent such as sulphite. This reduces the iodine formed in the reaction to iodide and enables equimolar proportions of iodide and gold salt to be used. Under safelight conditions 1.5 cc. of a lmolar potassium sulphite solution is mixed with 1 cc. of 10 percent gum arabic and 1 cc. of 1.5 molar potassium iodide. 3 cc. of 0.5- molar sodium auric chloride is rapidly added, then after 30 seconds 15 cc. of 10 percent gelatin is added. After mixing for 30 seconds the emulsion is coated, exposed and developed as described in example I, to yield a gold image in exposed areas of the element.

EXAMPLE 1 l The procedure of example 10 is followed but a 10 percent solution of a copolymer of N- (3- thiabutyl)acrylamide and 3- acryloxypropanel-sulphonic acid sodium salt (ratio l:9) is used in place of the gum arabic. Similar results are obtained.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

What is claimed is:

1. A photosensitive emulsion which comprises a dispersion of photosensitive aurous iodide, as the sole photosensitive component, in a hydrophilic colloid.

2. A photosensitive emulsion as defined in claim 1 wherein the hy drophilic colloid is gelatin.

3. A photosensitive element which comprises a support carrying a layer of dispersion of photosensitive aurous iodide, as

' the sole photosensitive component, in a by drophilic colloid.

4. A photosensitive element as defined in claim 3 wherein the hy drophilic colloid is gelatin.

5. A photosensitive element as defined in claim 3 wherein the aurous iodide is coated on the support at a coverage of between 20 and 800 milligrams of aurous iodide per square foot of support.

6. A photosensitive element as defined in claim 3 wherein the aurous iodide is coated on the support at a coverage of between 40 and 400 milligrams of aurous iodide per square foot of support.

7. A photosensitive element which comprises a photographic support and a layer of a photosensitive emulsion comprising a dispersion in gelatin of photosensitive aurous iodide grains as the sole photosensitive component, the aurous iodide being present on the support at a coverage of between 40 and 400 milligrams of aurous iodide per square foot of support.

8. A process for photographic reproduction which comprises imagewise exposing to actinic radiation an element comprising a support carrying a dispersion of photosensitive aurous iodide, as the sole photosensitive component, in a hydrophilic colloid to form a latent image, and developing a gold image in exposed areas of the element by contacting the element with a solution of a developer therefor.

9. A process as defined in claim 8 wherein the developer solution is selected from the group consisting of polyhydroxybenzene developer solutions, aminophenol developer solutions and hypophosphorous acid developer solutions.

10. A process as defined in claim 8 wherein the aurous iodide is coated on the support at a coverage of between and 800 milligrams of aurous iodide per square foot of support.

11. A process for photographic reproduction which comprises imagewise exposing to actinic radiation a photographic support carrying a layer of a photosensitive emulsion compris ing a dispersion in gelatin of aurous iodide grains as the sole photosensitive component of the emulsion, the aurous iodide being present on the support at a coverage of between 40 and 400 milligrams of aurous iodide per square foot of support, and developing a gold image in exposed areas by contacting the emulsion with a solution of a developer therefor.

12. A process for photographic reproduction which comprises imagewise exposing to actinic radiation a photosensitive element comprising a support carrying a layer of a dispersion of photosensitive aurous iodide, as the sole photosensitive component, in a hydrophilic colloid, contacting the element with a solution of a developer therefor and transferring unexposed, undeveloped aurous iodide from unexpected areas of the element to a receiving sheet by contacting the element with the receiving sheet in the presence of the developer solution to develop a gold image on the receiving sheet.

13. A process as defined in claim 12 wherein the developer solution is selected from the group consisting of polyhydroxybenzene developer solutions, aminophenol developer solutions and hypophosphorous acid developer solutions.

14. A process as defined in claim 12 wherein the aurous iodide is coated on the support at a coverage of between 20 and 800 milligrams of aurous iodide per square foot of support.

15. A process as defined in claim 12 wherein the support is coated with a dispersion of aurous iodide in gelatin at a coverage of between 40 and 400 milligrams of aurous iodide per square foot of support, and the developer solution is a hypophosphorous acid developer solution. 

2. A photosensitive emulsion as defined in claim 1 wherein the hydrophilic colloid is gelatin.
 3. A photosensitive element which comprises a support carrying a layer of dispersion of photosensitive aurous iodide, as the sole photosensitive component, in a hydrophilic colloid.
 4. A photosensitive element as defined in claim 3 wherein the hydrophilic colloid is gelatin.
 5. A photosensitive element as defined in claim 3 wherein the aurous iodide is coated on the support at a coverage of between 20 and 800 milligrams of aurous iodide per square foot of support.
 6. A photosensitive element as defined in claim 3 wherein the aurous iodide is coated on the support at a coverage of between 40 and 400 milligrams of aurous iodide per square foot of support.
 7. A photosensitive element which comprises a photographic support and a layer of a photosensitive emulsion comprising a dispersion in gelatin of photosensitive aurous iodide grains as the sole photosensitive component, the aurous iodide being present on the support at a coverage of between 40 and 400 milligrams of aurous iodide per square foot of support.
 8. A process for photographic reproduction which comprises imagewise exposing to actinic radiation an element comprising a support carrying a dispersion of photosensitive aurous iodide, as the sole photosensitive component, in a hydrophilic colloid to form a latent image, and developing a gold image in exposed areas of the element by contacting the element with a solution of a developer therefor.
 9. A process as defined in claim 8 wherein the developer solution is selected from the group consisting of polyhydroxybenzene developer solutions, aminophenol developer solutions and hypophosphorous acid developer solutions.
 10. A process as defined in claim 8 wherein the aurous iodide is coated on the support at a coverage of between 20 and 800 milligrams of aurous iodide per square foot of support.
 11. A process for photographic reproduction which comprises imagewise exposing to actinic radiation a photographic support carrying a layer of a photosensitive emulsion comprising a dispersion in gelatin of aurous iodide grains as the sole photosensitive component of the emulsion, the aurous iodide being present on the support at a coverage of between 40 and 400 milligrams of aurous iodide per square foot of support, and developing a gold image in exposed areas by contacting the emulsion with a solution of a developer therefor.
 12. A process for photographic reproduction which comprises imagewise exposing to actinic radiation a photosensitive element comprising a support carrying a layer of a dispersion of photosensitive aurous iodide, as the sole photosensitive component, in a hydrophilic colloid, contacting the element with a solution of a developer therefor and transferring unexposed, undeveloped aurous iodide from unexposed areas of the element to a receiving sheet by contacting the element with the receiving sheet in the presence of the developer solution to develop a gold image on the receiving sheet.
 13. A process as defined in claim 12 wherein the developer solution is selected from the group consisting of polyhydroxybenzene developer solutions, aminophenol developer solutions and hypophosphorous acid developer solutions.
 14. A process as defined in claim 12 wherein the aurous iodide is coated on the support at a coverage of between 20 and 800 milligrams of aurous iodide per square foot of support.
 15. A process as defined in claim 12 wherein the support is coated with a dispersion of aurous iodide in gelatin at a coverage of between 40 and 400 milligrams of aurous iodide per square foot of support, and the developer solution is a hypophosphorous acid developer solution. 